An x-ray diffraction apparatus typically includes an x-ray source which comprises a sealed tube including an electron gun and a target such as molybdenum or copper which generates x-rays when bombarded with electrons from the electron gun. The x-rays emerge from a pin hole in the sealed source unit, and a separate shutter unit is generally located adjacent the source unit to isolate the source unit when necessary for safety reasons. The shutter unit is located between the source and a monochromator. The x-ray source typically generates a wide spectrum of frequencies, and the monochromator is a filter provided to filter the x-rays to obtain a beam of a single frequency for irradiating the sample. A collimator comprising a metal tube collimates and directs the beam at the sample. The collimator controls the flux and divergence of the beam incident on the sample.
The source and shutter are typically mounted and the source is rotatable about an axis. The source and shutter are also moveable along the axis of rotation. The source can thereby be moved to vary its attack angle and maximise the flux which is incident on the sample. However, once the source has been adjusted to the optimum position for maximum flux, it is then necessary to align the monochromator and collimator to direct the flux onto the sample. The collimator must be aligned in two directions, and must be angled correctly. The known system is difficult to adjust accurately and reliably, due to the large number of different variables to be adjusted to obtain the optimum flux on the sample.